Method of impregnating wood



w. c. ZELLER METHOD 0F IMPREGNATING WOOD original Filed Deb. a, 192:5

Feb. 24, 19.25.

Feb. 24h i925.

METHOD OF JNIEREGNATING WOOD.

Application filed December 8, 1923, Serial To all 'whom t may concern:

Be it known that l, WILLIAM C. Znnnnn, a citizen ot the United States, and a resident oi Perth Amboy, county of Middlesex, and

State oi New Jersey, have invented certain new and useful improvements in Methods of lmpregnating VVood7 of which the following` is a specification.

This invention relates to an improved 10 method ot treating wood so that it is impregnated with a preservative, this treatment being designed to drive the preservation into the wood the desired distance Jfrom the surface and to do this thoroughly7 in a comparatively short time as compared with previous methods. The method also accomplishes the impregnation with a relatively small amount of preservative delivered to the wood thereby reducing to a great extent the pumping of the preservative to the retort and returning it to its source of supply.

The invention also relates to an apparatus for carrying out the method and also certain details of construction which will be hereinafter more fully described and finally embodied in the claims.

A Jform of apparatus for carrying out the invention is illustrated in the accompanying drawings, in which Figure 1 is a diagrammatic view of a retort with poles in it and also showing accessories and mechanism Jfor applying the steps in the method. Figure 2 is a detail cross section of the top of as the retort and one oi the spraying pipes.

I employ any ot the usual forms ot retort 10 into which the poles 11 or other wooden articles to be impregnated are placed. The usual way to place and support them is to lo place them on trucks 12 which are rolled from outside tracks through one of the ends of the retort. The ends are closed by the doors or end plates 13 and are properly packed or provided with gaskets to make 45 the retort air tight when the doors are shut.

in the form shown the poles are in two sets with the but-t ends or lower ends together and thus are disposed so as to be under the spraying or drenching pipe 14.

An air pipe line 15 is connected to the spray pipe 14 and to the air receiver 16 and has a valve 17 therein. The air receiver is equipped with a heating coil 18 and is connected by the pipe 19 to the air compressor 55 20. The pipe 19 has a valve 21 to control No. 679,336. Renewed Beceinber 12, 1924.

the amount of air admitted to the air receiver.

The supply pipe 22 supplies preservative to the retort and enters pipe 15 beyond the valve 17 and has a valve 23 to contr-ol the passage ot preservative through it. rlihe supply pipe can be ted directly from the hydrauli'e pump 24 through the pipe 25 and valve 26 or by pipe 27 and pipe 28 from the supply tank 29 which contains the preservative. The pipe 27 has a valve 30 and the pipe 28 has a valve 48 and extends to feed the hydraulic pump 24 and is provided with a valve 31 beyond the pipe 27. The supply tank 29 is supplied with a heating coil 32 to keep the preservative at the proper temperature.

The drain pipes 33 conduct preservative from the retort 10 to the supply tank 29 and are provided with valves 84. The drain pipes are usually placed on opposite sides of the centre ofi the retort.

A steam pipe 35 having a valve 36 is used to supply live steam to the retort and the reliet pipe 37 has the valve 3S and is used lor relieving the pressure on the retort when desired.

The vacuum pump 39 is connected to the retort by the pipe 40 which is equipped with the valve 41.

The blow-oil pipe is represented at 42 and has a valve 43 to control the relief of the retort when necessary.

In treating poles or piles and similar articles it is sometimes advisable to treat the whole pole and on the other hand it is sometimes only necessary to treat a part ot its length with preservative as in telephone or similar poles. In other cases piles are treated only at that part on the water line or between high and low water lines and in these 'cases the spray pipe directs preservative only7 on those parts to be treated. To tit l such cases ll make the spray pipes 14 interchangeable and l show them screwed into the 'iF-joint 44 and having the openings 45 so that the preservative can pass from the pipes to the retort. lin full lines l show pipes 14 to treat only the butt ends of the poles 11 but l may make the pipes longer as at 14, and it will be evident that shorter pipes may be used or pipes with the perforatlons 45 at only separated points so as to treat intermediate points in the length of the poles. I prefer to make the openings 45 in the orm of cuts in the top of the spray pipes 14 so that the preservative is ejected in a fan shape and is thus spread more evenly by hitting the top of the retort lirst and then is splashed on the poles, as will be evident from Figure 2. The ends of the spray pipes are closed so that all the preservative is projected laterally from the pipes.

The retort is heated by a suitable heating coil which is indicated at 46. I will now proceed to describe the operation of the method using the mechanism shown herein to illustrate the various steps. In the initial preparation of wood which initial preparation is no part of this invention and is not new but which is embodied herein to make the description complete, the material is usually subjected to live steam at a pressure of about twenty pounds per square inch for a period of from one to four hours or perhaps longer this depending on whether the material is green or partly seasoned. To carry out this steaming treatment, the valve 36 is opened allowing steam to flow from the steam supply pipe 35 into the retort 10. During this steaming period the condensation inside the retort is allowed to escape through the blow-oft1 valve 43 and through pipe 42 all other valves being closed during the steaming period. At the conclusion of the steaming period the valve 36 is closed and the blow-off valve 43 open fully so that the retort can be fully drained of condensation and when fully drained the valve 43 is again closed.

The other valves remain closed and the valve 41 is now opened and the vacuum pump 39 is operated so that the pipe 4() permits the vacuum pump to exhaust the air from the inside of the retort so that the air is exhausted to a minimum of some twenty-tvvo to twenty-tive inches of mercury. During both the steaming and vacuum periods the desired temperature is maintained inside the retort 10 by the heating coil 46. After the vacuum treatment has been continued for the desired length of time and the air is extracted from the pores ot the wood the vacuum pump is stopped and the valve 41 is closed.

With the retort thus under vacuum the valves 23, 30 and 48 are open and preservative from the tank 29 flows through the pipes 28, 27 and 22 and the end of pipe 15 into the spray pipe 14 and from it is delivered onto the surface of the wood and completely drenches that portion of the wood to be impregnated, the preservative entering freely` into the wood as the retort is still under vacuum and there is no resistance from inside of the wood to a substantial penetration of the pores. It will be observed that only that part of the Wood is drenched that is covered by the spray pipe 14 so that the drenching is localized to the part of the timber that is underneath the spray pipe. If greater or less material in the direction of length is to be drenched, the pipe 14 is unscrewed from the T-joint 44 and replaced by one of the proper length or by one in which the outlets 45 are grouped or placed where the drenching is to take place. In the illustration it will be observed that the butt ends of the poles 11 are the parts that are to be impregnated.

rIhe preservative iowing into the retort slowly exhausts the vacuum and when it is exhausted the valves 23, 30 and 48 are closed shutting off the supply of liquid preservative. The liquid preservative not absorbed by the wood while under vacuum is drained out of the retort 10 into the liquid preservative supply tank 29 through pipes 33 by opening valves 34 proper vent being given by opening valve 38 which as soon as the draining is complete is again closed.

Valves 23, 26, 31 and 48 are now opened, all other inlet valves being closed, and the valve 34 being left open and the surface of the wood inside the retort 10 is again subjected to a drenching with the liquid preservative supplied by the pump 24 which delivers it through pipe 22 and the end of pipe 15 and the spray pipe 14, the preservative passing from the supply tank 29 to the pump 24 through pipe 29 the excess preservative from the retort returning from the supply tank 49 through the drain pipes 33.

This preservative is supplied at a temperature of 17 5 to 200 degrees Fahrenheit being maintained at the proper temperature by the heating coil 32. This drenching it will be noted takes place at atmospheric pressure and fills those pores which have been partly vacated by the absorption by the wood. After the drenching of the portion of the timber that is to be impregnated with liquid preservative at atmospheric pressure, the valves 17 and 21 are opened all other valves boing closed and compressed air is fed from the air compressor 20 through the air receiver 16 and pipe 15 to the retort. The heating coil 18 in the air receiver 16 heats the air in the receiver it being customary to deliver this air to the retort at a temperature of to 120 degrees Fahrenheit.

rIhis air pressure is built up inside the retort from ten to one hundred pounds pressure per `square inch. During the building up of this air pressure in the retort the liquid preservative already absorbed by the wood is forced to a deeper penetration into the pores of the wood. When one hundred pounds air pressure per square inch is obtained inside the retort the air compressor 2O is stopped and the valves 17 and 21 are closed.

In order to facilitate from this point the impregnation of the wood and, drive the preservative 'further into it I torce liquid preservative into the retort against the one hundred pounds air pressure by means ot the hydraulic pump 24 and as the valves 26 and 23 are opened and the valve l? is closed, the preservative is draivn from the supply tank 29 and as valves 3l and 48 are also open, this provides i'or pumping the preservative against the air pressure and delivering it to the Wood u'hile the retort is under the pressure.

The injection of this preservative into the retort increases the pressure to a slight extent. During this operation the valves 34 are so adjusted that the liquid preservative not absorbed by the Wood can pass through the pipe 33 to the tank 29 but not to the full extent as care is taken to retain the small amount of liquid in the bottom of the retort 10 as shown at 47 in the drawing which acts as a seal and prevents the escape ot air trom inside the retort l() and which also assists in slightly building up the pressure Within the retort.

The level of the quantity of this preservative at the bottom of the retort is retained belouT the Wood that is beinlg impregnated. The level of the liquid preservative in the tank can be observed from any ot the ordinary depth gages with which the retort can be equipped.

When the Wood has absorbed the desired amount of liquid preservative the hydraulic pump 24 is stopped, valves 23, 26 and 48 are closed and the liquid preservative inside the retort is then allowed to iioiv into the liquid preservative supply tank 29 through pipes 33 by opening valves 34 to the full extent. After the retort has been fully drained oi: liquid preservative the relief valve 38 is opened allowing the air pressure in the retort to escape through pipe 37.

Except for the steaming process the several operations described hereinbefore can be repeated as often as desired.

I tind in this process and by the use ot this apparatus, that the penetration of the liquid preservative into the Wood is facilitated by the successive applications of preservative, iirst in a vacuum, then in the presence of atmospheric pressure and then in a pressure considerably in excess of atmospheric pressure.

When impregnation of the Wood is accompli-shed by a longer pipe such as 14a, a detachable outlet pipe 49 is attached to the inner end ot the pipe 33 so as to bring the opening of the .outlet pipe substantially in line With the end ot the inlet pipe.

It will also be noted that when atmospheric pressure is being built up in the retort the valve 23 can be opened slightly to permit the hydraulic pump 24 to feed a small quantity of preservative to the air passing into the retort. Such small application of preservative with the air assists in coating the Wood with preservative which makes it easier for the preservative When it is admitted in full volume to enter the Wood in contrast With such application ot the preservative to the Wood in the presence of a high air pressure through Which it must penetrate.

I claim:

1. A method ot impregnating Wood which comprises subjecting the Wood While in a closed retort to a vacuum treatment, then applying preservative to the Wood until the vacuum is exhausted, then building up an air pressure in the retort to torce the preservative on the Wood into the pores thereof and then subjecting the Wood to more preservative While the air pressure in the retort is maintained.

2. A method of impregnating Wood which comprises subjecting the Wood While in a closed retort to a vacuum treatment, then applying preservative to the Wood until the vacuum is exhausted, then drainintg oft' any excess preservative in the retort, then subjecting the Wood to preservative While under atmospheric pressure.

3. A method ot impregnating Wood consisting in applying preservative to the Wood in a partial vacuum, then applying preservative in atmospheric pressure, and then applying preservative in a pressure in excess of atmospheric.

4. A method ot impregnating a pole for a part of its length consisting in placing the Whole pole in a retort, placing the Who-le retort under a vacuum, applying preservative to that part of the pole to be treated, relieving the vacuum, building up an air pressure in excess of atmospheric pressure and then applying preservative to the part of the pole to be treated While the pressure in the retort is maintained in excess of atmospheric pressure.

In testimony that I claim the foregoing, I have hereto set my hand, this 7th day of December, 1923.

WILLIAM C. ZELLER. 

